CVE-2023-1637 in Linux
Summary
by MITRE • 03/28/2023
A flaw that boot CPU could be vulnerable for the speculative execution behavior kind of attacks in the Linux kernel X86 CPU Power management options functionality was found in the way user resuming CPU from suspend-to-RAM. A local user could use this flaw to potentially get unauthorized access to some memory of the CPU similar to the speculative execution behavior kind of attacks.
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Analysis
by VulDB Data Team • 08/11/2025
This vulnerability resides within the Linux kernel's x86 CPU power management subsystem, specifically affecting the boot CPU's handling of speculative execution behaviors during suspend-to-RAM resumption. The flaw manifests when the system resumes from a suspended state, creating a window where speculative execution mechanisms can be manipulated to potentially access unauthorized memory regions. This represents a sophisticated attack vector that exploits the complex interaction between power management states and CPU microarchitecture features. The vulnerability is classified under CWE-119 as a weakness related to memory access violations during system state transitions. The issue stems from inadequate validation of CPU state consistency during the resume process, particularly when the boot CPU returns from suspend-to-RAM states. Attackers can leverage this flaw to perform side-channel attacks that exploit speculative execution behaviors similar to those seen in Spectre and Meltdown vulnerabilities. The local user privilege requirement indicates that exploitation does not require network access but rather physical or logical access to the target system. This vulnerability directly impacts the security boundary between different CPU execution states, potentially allowing attackers to extract sensitive information from memory regions that should remain protected during suspension. The attack surface is particularly concerning because it operates at the kernel level during critical system transitions, where normal security mitigations may be temporarily disabled or less effective.
The technical implementation of this vulnerability exploits the timing and state management aspects of CPU power management during the resume process. When a CPU resumes from suspend-to-RAM, it must reinitialize various microarchitectural state components including branch predictors, cache structures, and speculative execution buffers. The flaw occurs when these components are not properly invalidated or reinitialized during the transition, creating opportunities for speculative execution to access stale data. This behavior aligns with the ATT&CK technique T1059.001 for command and scripting interpreter usage, as attackers may leverage the compromised CPU state to execute malicious code through speculative execution pathways. The vulnerability is particularly dangerous because it operates at the intersection of hardware-level power management and software-level security controls, making traditional software-based mitigations insufficient. The attack can potentially expose sensitive kernel memory, including cryptographic keys, credentials, and other confidential data that may have been cached in CPU buffers during the suspended state. This represents a significant threat to systems where the boot CPU handles critical security functions, as the compromised state could allow attackers to gain access to system-wide secrets.
The operational impact of this vulnerability extends beyond simple information disclosure, potentially enabling more sophisticated attacks that could compromise entire system security. A successful exploitation could allow attackers to perform cache side-channel attacks that extract data from other processes or even from the kernel itself, effectively bypassing traditional memory protection mechanisms. The vulnerability affects systems that utilize suspend-to-RAM functionality, which is common in laptops, servers, and embedded systems where power management is critical. This creates a widespread impact across various computing environments, from consumer devices to enterprise infrastructure. The attack complexity is relatively low for local users who already have system access, making this vulnerability particularly concerning for environments with shared or untrusted access. Organizations using systems with Intel or AMD x86 processors that support power management features are at risk, especially those running Linux kernels that have not implemented appropriate mitigations. The vulnerability's impact is compounded by the fact that modern systems increasingly rely on speculative execution for performance optimization, creating more opportunities for exploitation. This flaw demonstrates the inherent complexity of securing modern CPU architectures where performance optimizations can create security vulnerabilities. The attack could potentially be chained with other vulnerabilities to escalate privileges or extract additional sensitive information from the system's memory space.
Mitigation strategies for this vulnerability should focus on both kernel-level patches and hardware-level protections. The primary defense involves implementing proper CPU state validation and invalidation during suspend-to-RAM transitions, ensuring that speculative execution buffers are properly cleared before system resume. System administrators should apply kernel updates that include mitigations for speculative execution vulnerabilities, particularly those addressing the specific power management state transitions. The implementation should include proper microcode updates from CPU vendors, as many of these vulnerabilities are addressed through hardware-level fixes that prevent the problematic speculative execution behaviors. Organizations should consider disabling unnecessary power management features when security is a primary concern, particularly in high-value environments where the risk of exploitation is elevated. Monitoring for anomalous CPU behavior during system transitions can help detect potential exploitation attempts, though this requires sophisticated logging and analysis capabilities. The security community should also consider implementing additional runtime protections that can detect and prevent malicious use of speculative execution during system state transitions. Regular security assessments should include testing for these types of vulnerabilities, particularly in environments where systems frequently enter and exit suspend states. This vulnerability highlights the importance of continuous security evaluation of system components, especially those that operate at the intersection of performance optimization and security controls, as the complexity of modern computing architectures creates new attack surfaces that traditional security approaches may not adequately address.